1. Field of the Invention
The present invention relates to a leak detector for attachment on a stuffing box of a rod pumped well. More particularly, the present invention relates to a leak detector with a reservoir for containing fluid leakage from around a polish rod liner which is located within the stuffing box. The reservoir is provided with a switch which is activated by a given level of fluid in the reservoir, said switch providing a means for shutting down the well's pump. Alternately or additionally, the switch can be utilized to send a signal remotely to notify an operator that the well needs attention.
2. The Prior Art
Preliminary searches were conducted on the invention disclosed herein, and the following patents were uncovered in the searches:
______________________________________ Pat. No. Inventor Issue Date ______________________________________ 3,270,810 Johnston Sept. 6, 1966 3,276,246 Truman, et al. Oct. 4, 1966 3,815,925 Mattoon June 11, 1974 3,914,752 Howard, et al. Oct. 21, 1975 3,955,822 Irby May 11, 1976 3,967,678 Blackwell July 6, 1976 4,135,859 Carson, et al. Jan. 23, 1979 4,516,911 Senghaas, et al. May 14, 1985 4,647,050 Johnson Mar. 3, 1987 4,917,190 Coppedge Apr. 17, 1990 4,951,743 Henderson Aug. 28, 1990 ______________________________________
Reciprocating rod arrangements are commonly utilized in connection with such devices as pumps and compressors acting on gases or liquids; for example, oil well pumping units where a polish rod is reciprocated within a wellhead by the up and down action of the pumping unit's horse head to which the polish rod is clamped.
Rod pumped wells have a packing gland system at the wellhead, commonly called a stuffing box, with seals or packing to prevent leakage from passing out of the stuffing box from around the reciprocating rod. The reciprocating rod in an oil well is commonly called a polish rod and is generally provided with a sleeve-type liner in the area of the stuffing box to protect the polish rod from wear caused by constantly rubbing against the seals or packing within the stuffing box.
Even though seals in a stuffing box may be very effective when new, as they wear, due to the reciprocating action of the rod or rod liner through the packing or seal, leakage will occur between the packing or seals and the rod or rod liner. Furthermore, while the extent of the leakage may not be sufficient to cause the well to be shut down in order to replace the seal or packing due to the associated reduction in production or potential damage to the equipment, even small amounts of leakage, i.e. oil, salt water, etc., into the surrounding environment creates a measurable amount of pollution.
Thus, frequent servicing of the packing or seal around the reciprocating rod liner becomes necessary to prevent leakage that would otherwise be considered inconsequential from an operational or economic standpoint. Thus, while it is known to provide stuffing boxes with leak detectors (see Truman, et al., U.S. Pat. No. 3,276,246), many such arrangements merely serve to stop operation of the well once excessive leakage occurs and do not deal with the leakage occurring under circumstances where except for the environmental and safety concerns there is no need to cease operations.
Even of these devices which detect excess leakage, some, such as U.S. Pat. No. 4,647,050 by Johnson and U.S. Pat. No. 4,917,190 by Coppedge, have only a visual indicator, such as a sight glass or pressure gauge, of leakage with no provision to automatically shut down the well's operation.
Some leak detectors, such as U.S. Pat. No. 4,135,859 by Carson, et al. have no visual means of detecting oil leakage other than disassembling the device. Inability of the operator to view the inside of the fluid retaining vessel without disassembling would limit the opportunity for preventive maintenance on the stuffing box seals.
The Carson patent also has another problem. The switch on this device is activated by the weight of liquid within a collecting reservoir. The weight of the liquid pulls on a spring and activates the switch. However, when exposed to a high vibration environment, this type of switch can be activated by the vibration alone, even without a sufficient amount of liquid in the reservoir to activate the switch, thus resulting in unnecessary down time of the well.
Installation and serviceability have been other problems with the prior art leak detectors. Some are not split assemblies and, therefore, require the polish rod to be disconnected from the horse head to allow the leak detector to be installed, serviced, or replaced. A good example of a leak detector having this installation problem is U.S. Pat. No. 3,967,678 by Blackwell.
The Blackwell patent also illustrates another problem with some prior art leak detectors. The Blackwell leak detector adds considerable length to the stuffing box assembly which can interfere with the reciprocation of the polish rod.
Durability has also been a problem with prior art leak detectors For example, U.S. Pat. No. 3,270,810 by Johnston, which appears to be made of sheet metal, would be unable to support the weight of the rod and would probably be ruined if the rod accidentally dropped onto it.
Another example of a leak detector with durability problems is U.S. Pat. No. 4,951,743 by Henderson. The Henderson patent provides a bellows-type containment around the polish rod which expands and contracts with each reciprocation of the polish rod. Such continued folding and unfolding of the bellows would eventually result in a breach of the containment which would require replacement of the bellows.
The remaining patents listed above are not considered sufficiently pertinent to require comment.
The present invention overcomes the shortcomings of the prior art by providing a split assembly adapter which can be easily and securely installed onto the stuffing box without adding significant length to the stuffing box. The split nature of the adapter allows the complete leak detector to be removed prior to major workovers, thus minimizing the chance of damage to any part of the leak detector. The adapter, machined from steel or made from other suitably rigid material, is sufficiently rugged to support the weight of the polish rod or to withstand the impact of a rod string dropping onto it.
The adapter is attached to a reservoir holder containing electrical connections; a fluid reservoir removably attaches to the reservoir holder. The reservoir holder can be detached from the adapter without disturbing any of the electrical connections, thus minimizing the possibility of damage during periodical work on the well, such as changing out the downhole pump or pulling rods to replace a broken rod.
The invention has a transparent or translucent fluid reservoir which enables the operator to see when he needs to perform preventive maintenance but which prevents leakage contained within the fluid reservoir from entering the surrounding environment. The invention's reservoir is provided with a long travel float-type switch which can be used to terminate operation of the well when activated. This float-type switch is not as susceptible to variation in point of activation caused by vibration as are weight activated switches.